Display/layout methods and apparatuses including content items and display containers

ABSTRACT

Methods and apparatuses for generating rendering layout specifications for content items to be rendered, using display containers, and/or rendering the content items using the generated rendering layout specification are disclosed. In various embodiments, the generating of a rendering layout specification may include one or more of selecting a display container for a content item, selecting a content item for a display container, and selecting a display container for a display container.

RELATED APPLICATIONS

The present application is a non-provisional application of provisionalapplications 60/628,448 (filed on Nov. 16, 2004), 60/628,194 (filed onNov. 16, 2004) and 60/636,495 (filed on Dec. 16, 2004), and claimspriority to the three enumerated provisional applications.

TECHNICAL FIELD

Embodiments of the present invention relate to the field of dataprocessing, in particular, to layout and/or rendering methods andapparatuses.

BACKGROUND

Notwithstanding the significant advances made in the past decades, Weband print publishing technology continue to suffer from a number ofdisadvantages preventing users from fully realizing the benefits thatmay flow from advances in computing and related technology.

For example, current publishing technology is unable to flexiblyaccommodate content items of different sizes within displaypresentations. Specifically, most Web sites continue to be unable toallow display of content items of different sizes, such asadvertisements of different sizes, to appear in a given position withina Web page, without incurring unacceptable layout effects, such asoverlapping of content items, internal wasted space, unreadable text,and so forth.

Another example is current publishing technology failing to take fulladvantage of the available area of display presentations to displayinformation. Specifically, Web sites cannot take full advantage ofavailable area of client browser windows to display content items, suchas advertisements. Client browser windows often use a variety of screenresolutions and window sizes. To accommodate the largest number ofpotential viewers, Web pages are typically authored using small fixedwidths. As a result, the majority of clients can view the Web pageswithout horizontal scrolling. But then clients with larger displays haveunused real estate. HTML and CSS allow Web pages to be authored withpercent widths, so that HTML/CSS Web pages stretch to fit large clientdisplay widths. However, layouts with percent widths can generateinternal wasted real estate. Even if no real estate is wasted, percentwidths do nothing to use increased real estate for additionalinformation display.

Still another example is the manner current publishing technologyhandles situations where there's more information to display than willfit in a display presentation. Current Web technology providesfacilities to allow scrolling in the display window, for the users toaccess the information that did not fit in the display window.Specifically, Web browsers provide horizontal and/or vertical scrollbarsin situations where a Web page to be displayed is larger in at least onedimension than the Web browser window. Some Web sites use downloadablescripts that affect information display within a particular region ofthe page, so that more information may be cycled through this regionthan will fit in the region all at once. Some of these sites fitformatted or unformatted text into the region, according to the region'sdimensions as determined by standard HTML/CSS layout rules, with textlayout sensitive to the reader's specified preferences for suchparameters as number of columns. For these sites, the reader may directsuccessive portions of a text flow to appear within the designatedregion, so that the successive renderings of the region are analogous topages of a printed document. However, there's currently no way to cyclecontent items through multiple regions of a display window whilemaintaining paged presentations in one or more regions of the window,while not requiring the cycled content items to conform to fixed regionsizes, and while allowing all information to be visible in the displaywindow without scrolling. One consequence is severely limitedpossibilities for displaying advertising in Web-based periodicals.

Still another example is the limited ability of current Web technologyto accommodate changes to displayed constituents that occur as the userviews the display. Currently, constituents can replace otherconstituents in regions with fixed dimensions, where the old constituentand new constituent have approximately the same fixed dimensions. It'salso currently possible for constituents to appear into what wouldotherwise be empty space, and for constituents to expand into emptyspace. Conversely, it's currently possible for constituents to bereplaced by empty space, and for constituents to shrink so that part ofthe area they formerly occupied becomes empty space. Further, it'scurrently possible to expand into and shrink from empty space through aripple effect applying along a single dimension. For example, given avertical column with multiple constituents and empty space on thebottom, if a constituent that's not at the bottom expands, theconstituents that lie below it can shift downward accordingly, with acorresponding reduction of the amount of empty space at the bottom ofthe column. Outside these bounds, with current Web technology, changesto displayed constituents are liable to incur unacceptable layouteffects, such as overlapping of content items, internal wasted space,unreadable text, and so forth.

Grid-based templates have long been a standard basis for specifyingfamilies of layouts. More recently, container-based templates havebecome a standard basis for specifying families of Web layouts. Forexample, current server page technology allows dynamic content to bedirected to HTML containers, such as tables, or to specific slots inHTML containers, such as table cells. Current Web authoring models,current automated tools for authoring print layouts, and currenttechnology for serving dynamic Web content are all limited by theirreliance on variants of the template model.

Above are just examples and not all the disadvantages and/or problemsaddressed by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described by way ofexemplary embodiments, but not limitations, illustrated in theaccompanying drawings in which like references denote similar elements,and in which:

FIG. 1 illustrates the concept of a world-within hierarchy in thecontext of the present invention, in accordance with variousembodiments;

FIG. 2 illustrates the concept of a container tree in the context of thepresent invention, in accordance with various embodiments;

FIG. 3 illustrates an overview of the display methods and apparatuses ofthe present invention, in accordance with various embodiments;

FIGS. 4-6 illustrate selected operations of the layout generator of FIG.1, in accordance with various embodiments;

FIG. 7 illustrates an example computer system, suitable for use tofacilitate practice of the present invention, in accordance with variousembodiments;

FIGS. 8 a-8 c illustrate an example problem the present invention may beapplied to address, which is to permit full use of the available areasof computer display windows;

FIGS. 9 a-9 c illustrate an example application of the present inventionto accommodate display items of different sizes within computer displaywindows; and

FIGS. 10 a-10 f illustrate an example application of the presentinvention to permit information display in computer display windowswithout scrolling.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Illustrative embodiments of the present invention include but are notlimited to display layout generation and rendering methods andapparatuses, in particular, display layout generation and renderingmethods and apparatuses that employ display containers.

Various aspects of the illustrative embodiments will be described usingterms commonly employed by those skilled in the art to convey thesubstance of their work to others skilled in the art. However, it willbe apparent to those skilled in the art that alternate embodiments maybe practiced with only some of the described aspects. For purposes ofexplanation, specific numbers, materials, and configurations are setforth in order to provide a thorough understanding of the illustrativeembodiments. However, it will be apparent to one skilled in the art thatalternate embodiments may be practiced without the specific details. Inother instances, well-known features are omitted or simplified in ordernot to obscure the illustrative embodiments.

Further, various operations will be described as multiple discreteoperations, in turn, in a manner that is most helpful in understandingthe illustrative embodiments; however, the order of description shouldnot be construed as to imply that these operations are necessarily orderdependent. In particular, these operations need not be performed in theorder of presentation.

The phrase “in one embodiment” is used repeatedly. The phrase generallydoes not refer to the same embodiment; however, it may. The terms“comprising,” “having,” and “including” are synonymous, unless thecontext dictates otherwise. The phrase “A/B” means “A or B”. The phrase“A and/or B” means “(A), (B), or (A and B)”. The phrase “at least one ofA, B and C” means “(A), (B), (C), (A and B), (A and C), (B and C) or (A,B and C)”. The phrase “(A) B” means “(B) or (A B)”, that is, A isoptional.

Illustrative embodiments of the present invention will be describedusing terms such as “content items,” “display presentations,” “displayunits,” “containers,” “flows,” and “display pages.” For the purpose ofthe present invention, a “content item” is a piece of content that'sperceived as self-contained, and that contains no smaller piece ofcontent that's perceived as self-contained. Advertisements and newsarticles are two examples of content items. When an advertisementconsists of an image and a caption, the caption by itself wouldtypically not considered as a content item. Instead, the advertisementin its entirety would be considered a content item. Content items may bespecified by users, by the staff of service providers, programmatically,or through a combination of user input, staff input, and the effects ofprograms.

A “display presentation” may occupy a computer display window, or aprinted page, or a contiguous region within a computer display window ora printed page. Within a given display presentation, each content itemcorresponds to a “display unit.” As a matter of convenience, whenthere's no possibility of confusion, a display unit may be identifiedwith its corresponding content item.

A “display unit” is typically a single contiguous region with fixedshape and size. However, display units with variable shapes and sizesare possible, and less commonly, so are display units that correspond todiscontiguous regions with specified interrelationships.

A “content item” may have rich internal structure. Treating aninternally complex content item as atomic is a matter of perspective andspecification. If an application calls for multiple perspectives,content items and their corresponding display units may exhibit“world-within” recursion: Top-level layout arranges top-level displayunits; top-level display units present “inner worlds” and are themselvessubject to internal layout. Any number of levels of world-withinrecursion is possible in principle, though in various embodiments, thenumber of levels is purposely kept small.

FIG. 1 illustrates the concept of a world-within hierarchy, inaccordance with various embodiments. (The arrows in FIG. 1 are shown forillustration purpose only, and they are not part of the representedlayout.) At the top level of the hierarchy, there are eleven displayunits, each shown with a sparse dot pattern. Two of the top-leveldisplay units present inner worlds. The display unit labeled “3”includes six second-level display units, each shown with a vertical linepattern. Similarly, the display labeled “6” includes four second-leveldisplay units, each shown with a vertical line pattern. Among the foursecond-level display units within the display unit labeled “6,” thesecond-level display unit labeled “6 a” itself presents an inner world,with four third-level display units, each shown with dense dot pattern.A display unit that presents an inner world might or might not derive inits entirety from an internal source.

Content may take the form of markup such as HTML or XML. Alternatively,content may take the form of application-internal data structures.Content may be found in a wide variety of sources, ranging from HTMLfiles on the public Web to binary files on a local computer. Content maybe generated by variety of applications and systems. Content may becached on the client and on servers. In various embodiments, a primaryserver may be employed to gather content from diverse sources. Theprimary server may be associated with a system of proxy servers wherecontent is cached in anticipation of client requests. [HTML=HypertextMarkup Language, XML=Extensible Markup Language.]

Given that content items are presented in display units, and alsorepresented in a hierarchical data structure such as markup, the term“container” as used herein has parallel meanings. In terms of display, acontainer of a display unit corresponds to a region that contains thedisplay unit. In terms of hierarchical data structures, a container of acontent item is a node that dominates the node corresponding to thecontent item. However, not every region that contains a display unitcounts as a container for the display unit. And not every node thatdominates the node corresponding to the content item counts as acontainer of the content item. Only some containing regions, and theircorresponding nodes, count as containers of a given display unit and itscorresponding content item. Containers for content items may beidentified explicitly or implicitly by data structure authors. Forexample, Web site publishers may identify containers in Web site markup.In an alternative scenario, containers for content items may beidentified explicitly or implicitly by end users. Mixed scenarios arealso possible.

Multiple possible containers for a given content item may be identifiedexplicitly or implicitly. For example, an advertisement within a Webpage might have a table near the top of the page as one possiblecontainer, and a different table on the left of the page as anotherpossible container. Default rules can specify how alternate containersare identified for content items for which no alternative containershave been given.

Containers may be assigned to higher-level containers within a containerhierarchy. It should be emphasized that the container hierarchy is anartifact of layout, while the world-within hierarchy reflectscoarser-grained or finer-grained perspectives on content. As withcontainers for content items, not every region that contains a containerC counts as a container of C. And not every node that dominates the nodecorresponding to C counts as a container of C. Only some containingregions, and their corresponding nodes, count as containers of C.Higher-level containers may be specified explicitly or implicitly in thesame scenarios as for bottom-level containers. Multiple possiblecontainers for a given container may be identified explicitly orimplicitly. Default rules can specify how alternate containers areidentified for containers for which no alternative containers have beengiven.

FIG. 2 illustrates a container tree, in accordance with variousembodiments. Container C_(3,1,1) includes the display units labeled “9”and “10.” Container C_(3,1) includes the display unit labeled “8,” andalso container C_(3,1,1). Container C₁ include the display units labeled“1” and “2.” Container C₂ includes the display units labeled “3,” “5,”and “7.” Container C₃ includes the display units labeled “4” and “6,”and also container C_(3,1). The root of the container tree is acontainer that includes container C₁, container C₂, container C₃, andthe display unit labeled “11.” The fill patterns of the display units inFIG. 2 indicate container membership. Also, each display unit is labeledwith its lowest container in parentheses.

A “template” is a configuration of containers that encompasses at leasttwo containers that can include display units. The configuration cantake the form of a tree or of some other data structure. For example,server pages are templates whose instantiations are DHTML trees. Atemplate-based approach can feature template selection, where a set oftemplates is available, and one or another template is selected based onsuch considerations as content to be accommodated or the parameters of atarget device. A template-based approach can feature recursive filling,where slots in higher templates are filled by lower templates. Atemplate-based approach can combine template selection with recursivefilling, so that sets of templates at various levels are available. Oneof the distinguishing characteristics of the present invention is thatit works without templates, and that it can efficiently generate largerranges of layouts than what's possible with template-based approaches.

In general, display units may overlap, as in a layered presentation.However, in many applications, display units will not be allowed tooverlap. Given that display units don't overlap, two bottom-levelcontainers C₁ and C₂ may still overlap, in the sense that the convexhull of the display units within C₁ overlaps the convex hull of thedisplay units within C₂. A similar observation applies at higher levelsof the container hierarchy. Containers may fit together like non-convexpuzzle pieces. For example, in FIG. 2, the convex hull of the displayunits in C₂ overlaps with the convex hull of the set of display units inC₃.

Given a container C, each child of C within the container hierarchy maybe called a “filler” of C and may be said to fill a “slot” of C. As arefinement of the assignment of content items to containers, contentitems may be assigned to specific slots within containers, andcontainers may be assigned to specific slots within higher containers. Aslot may correspond to an ordinal, as in the n^(th) slot of a container,or a slot may correspond to a tuple of ordinals, as when a table hasslots corresponding to row and column positions. It may or may not beallowed that in a completed layout a container's n^(th) slot is filledwhile its (n−1)^(th) is unfilled, and similarly for slots correspondingto tuples of ordinals. It might be stipulated that if slot n is filledwhile slot n−1 is unfilled, slot n−1 will appear with specifiedplace-holder content. Or slot n might simply be allowed to appear in theplace of slot with a lower assigned ordinal. Or the assignment ofcontent to slot n might be invalidated in the case when no content isassigned to slot n−1. Note that in the case of tables, if a row i has acell with assigned content, and column j has a cell with assignedcontent, then the cell that belongs to row i and column j will appear nomatter whether or not it has assigned content.

A “display entity” is either a container or a display unit. An“inner-outer pair” of display entities comprises an “inner member” andan “outer member,” where the inner member is a candidate for placementin the outer member. A “valid inner-out pair” is an inner-outer pairsuch that the inner member belongs to a class of display entities α andouter member belongs to a class of display entities β, where it'sstipulated that members of β are candidate containers for members of α.For example, an inner-outer pair where the inner member is a displayunit and the outer member is a container might be valid, but aninner-outer pair where the inner member is a container and the outermember is a display unit cannot be valid. For content items expressed inHTML, an inner-outer pair where the inner member is an image and theouter member is a table is valid, but not vice-versa. (Recall that acontainment relationship need not correspond to a parent-childrelationship in a markup tree.) An inner-outer pair where the innermember is a table and the outer member is a body is valid, but notvice-versa.

Content items may have associated layout rules. For example, a contentitem described in HTML has associated layout rules according to the HTMLstandard. Similarly, containers may have associated layout rules. Forexample, an HTML table has associated layout rules according to the HTMLstandard. Standard layout rules may be supplemented through markupextensions. For example, while the number of cells in a standard HTMLtable is fixed, markup extensions can specify that a given table mayhave a variable number of cells, and can specify how rows and columnsare added as the table receives more content. Default rules can specifyhow rows and columns are added to tables for which no extended markup issupplied.

A flow is a content item that comprises a sequence of subconstituents.Text runs are archetypical flows. In various embodiments, to qualify asa flow, a sequence of constituents is required to satisfy twoconditions. First, the sequence is required to be associated with a setof layout rules that determines the placement of successive items of thesequence. For example, the successive words and delimiters of Englishlanguage text runs are placed left to right on lines, with linesfollowing each other from top to bottom. Standard and non-standardtypographic rules may be in effect as refinements of these basic rules.The second required condition for a flow is that it may be “frangible.”“Frangible” is defined here in terms of display presentation. A sequenceof constituents is frangible if it can be divided into successivesubsequences, where each subsequence is large enough to be displayed onits own in a display region. In general, there will be many ways todivide a frangible flow into such subsequences. Standard typographicrules evolved for printing offer guidance on how to set the criteria fordetermining which subsequences are large enough for independent display.Such subsequences may be called “displayable sub-flows.” Besides textruns, other examples of flows include sequences of text and images, andother examples of flows include tables. For a sequence of text andimages, standard and non-standard typographic rules may allow images tobe reordered with respect to text elements, and with respect to eachother. For a table, it may be possible to display the table several rowsat a time, or several columns at a time.

A non-flow content item is “compatible” with a display region if itswidth is no greater than the width of the display window, and its heightis no greater than the height of the display region. A flow is“compatible” with a display region if it can be partitioned intodisplayable sub-flows such that each sub-flow can be laid out so thatthe sub-flow is fully visible within the display region. A set ofcontent items is “compatible” with a display region if all of itsmembers are compatible with the display region.

A “display page” for a given display region is a layout of content itemssuch that the horizontal and vertical dimensions of the layoutsubstantially match the dimensions of the display region. Note that adisplay region that receives display pages may be a proper sub-region ofa display window or a printed page. Paged presentations are not limitedto display windows and printed pages. Thus a display window maysimultaneously support multiple paged presentations in differentsub-regions.

The present invention permits a set of content items that's compatiblewith a display region to be displayed in the display region so that allcontent is visible without scrolling. Of course, in general it's notpossible to display all content items visibly within the display regionat the same time. Content items are therefore apportioned across a setof display pages, which are rendered into the display region one at atime. In various embodiments, each non-flow content item appears onexactly one display page. In various embodiments, a single non-flowcontent item may be allowed to appear on multiple display pages. Invarious embodiments, each flow may be partitioned into displayablesub-flows so that each sub-flow appears on exactly one display page. Invarious embodiments, a particular flow constituent may be allowed toappear on multiple display pages. In various embodiments, the displaypages may be unordered. In various embodiments, the display pages may bepartially ordered. In various embodiments, the display pages may belinearly ordered.

Referring now to FIG. 3, wherein a block diagram illustrating anoverview of the display layout generation and rendering methods andapparatuses of the present invention, in accordance with variousembodiments, is shown. As illustrated, for the embodiments, differentcombinations of content items 306 from a variety of sources, includingbut not limited to applications 302, content databases 304, may beprovided to layout generator 312 incorporated with the teachings of thepresent invention, to generate layout specifications 308 for layoutinterpreter 315 and render engine 316 to render content items 306 asdisplay presentations 310 on a display window or a printed page, or in aregion of a display window or printed page. Content items 306 may besingle or multi-media contents from a variety of sources including localand remote data sources, e.g. a remote Web site. Display windows orprinted pages, or regions of display windows or printed pages, may be ofvarious sizes, shapes and resolutions. For client displays,client-server bandwidth information may also be provided forconsideration. These media parameters may be provided to layoutgenerator 312 in a variety of manners, via specification files, functioncalls, and/or other means.

As illustrated, layout generator 312 employs a number of displaycontainers or simply containers 314 to generate layout specifications308 for content items 306. Display containers can be provided in generalor for a generation in particular. Containers 314 are assigned tocontent items 306 in combination based on what's appropriate or optimalfor a particular collection of content items to be displayed. Of course,what's appropriate or optimal is application dependent, in particular,dependent on the criteria employed to determine appropriateness oroptimality. Such criteria may vary from application to application orfrom implementation to implementation.

For the embodiments, layout generator 312 generates a layoutspecification 308 for a collection of content item 306 in accordancewith media parameters, layout guidelines, display containers and/orcriteria inputs 313 provided in general or for a generation inparticular. Except for media parameters, the layout guidelines, displaycontainers and/or criteria inputs 313 are typically (but notnecessarily) provided at a high or abstract level, providing generalguidance for layout specification generation in general or a particulargeneration. Layout guidelines and/or criteria inputs 313 may include butare not limited to, the target medium on which content items 306 willeventually be rendered (e.g. medium type, size, shape and so forth), thecontent containers to be employed, the size and/or shape of the contentcontainers, and criteria for determining whether a layout is to beconsidered acceptable (such as percentage of internal blank space).

Layout interpreter 315 performs the conventional function ofinterpreting layout specifications 308 and generating renderinginstructions (e.g. graphic function calls) for rendering engine 316 torender content items 306 as display presentations 310 on the targetedmedium, in accordance with layout specifications 308. Likewise,rendering engine 316 performs the conventional function of effectuatingspecific rendering instructions (such as graphic function calls) torender content items 306 as display presentations 310 on the targetedmedium.

While for ease of understanding, the functions performed by layoutgenerator 312, layout interpreter 315 and render engine 316 areillustrated as three distinct components. In practice, their functionsmay be partitioned and assigned to different smaller modules and/ortasks. And these tasks may be executed as a single thread, or asmultiple threads where appropriate. In various embodiments, theexecution of layout generator 312, layout interpreter 315 and renderengine 316 may be on the same system, and in other embodiments, they maybe on different systems, e.g. with layout generator 312 on a server, andlayout interpreter 315 and render engine 316 on a client device. Forthese latter embodiments, communication between layout generator 312 andlayout interpreter 315 may be in accordance with any one of a number ofcommunication protocols, including but not limited to HTTP and/or HTTPS,with or without going through one or more communication modules/layers(where HTTP=Hypertext Transmission Protocol, and HTTPS=HypertextTransmission Protocol Secured).

In various embodiments, layout generator 312, layout interpreter 315,and/or render engine 316 may be implemented as part of a “larger”product offering. For examples, in various embodiments, all threecomponents 312, 315 and 316 may be implemented as part of a Web Browseror a Print Driver. In still other embodiments, layout interpreter 315and render engine 316 may be part of a Web Browser, while layoutgenerator 312 may be part of a Web Server or a Publishing Tool.

FIGS. 4-6 depict selected operations of layout generator 312, inaccordance with various embodiments. In various embodiments, the layoutgenerator 312 is executed as a single thread to execute operations asfollows: identify the content items to be placed 402, order the contentitems 406, and lay out the content items in a set of linearly ordereddisplay pages 408. In various embodiments, for each display page, layoutgenerator 312 places the content items on the display page according tothe ordering of the set of content items 502-506. For each content itemto be placed 602, layout generator 312 identifies the possiblecontainers for the content item 604, order the containers, 606 and tryplacing the content item in the containers in order 608-618.

Content item placement may involve adjustments to the content itemitself 624, or to the container in which the content item is placed 610.Layout adjustments may percolate through the page 610. For example, anintermediate container may be created between the content item and thepreviously existing container, or the content item may convert fromabsolute to percentage sizing, or the content item may receive a bordertreatment. In this embodiment, placement of a single flow acrossmultiple display pages entails maintaining a cursor within the flow, sothat successive displayable sub-flows are assigned to successive displaypages. When the placement of a content item in a container is acceptable612 (and the display page layout is complete 626), or if the sequence ofcontainers is exhausted 614, layout generator 312 proceeds to the nextcontent item.

Thus, for these embodiments, the operations of layout generator 312 maybe considered as a nested loop with three levels: a display page loop(FIG. 5) contains a content item placement loop (FIG. 6) that contains acontainer placement loop (604-618). If the placement of a content itemin a container results in a display page layout that is deemed complete626, then both the content item placement loop and the containerplacement loop are exited immediately 628.

Various criteria for ordering content items are possible. For example,content items may be ordered based on their values, such as orderingadvertisements so that higher-priced advertisements are placed first.Various criteria for ordering containers are possible. For example,display containers may be ordered based on their remaining content itemholding capacity, such as ordering tables with unfilled cells beforetables without unfilled cells.

Various criteria for determining acceptable placements are possible. Forexample, if the placement of a content item in a container results in alayout that fits in the display region, so that no scrolling is requiredto view the entire layout, then that may be sufficient for the placementmay be deemed acceptable. It might be required in addition that thelayout of each display page satisfy criteria of consistency with thelayouts of previous display pages. Various criteria for deeming adisplay page layout complete are possible. For example, if thepercentage by area of blank space is below a stipulated threshold, thelayout may be deemed complete. Criteria for display page layoutcompleteness may reflect processing history, so that depending on howlayout has progressed, a layout that falls short of perfection by somecriteria is nevertheless deemed complete.

Various criteria are possible for deeming that the sequence of displaypages is complete. For example, if each successive display page includesa successive portion of a particular flow, the sequence of display pagesmay be deemed complete when the end of the flow has been assigned to adisplay page.

In other embodiments, the innermost loop is not exited when anacceptable placement of a content item in a container is found. Instead,the inner loop tries all placements of the content item at hand incandidate containers, compares the placements according to an objectivefunction, and finally places the content item in the preferredcontainer.

Other embodiments support layouts where content is not presented indisplay pages. If it isn't possible for all content items to be visiblein the designated display region at the same time, the display region isequipped with a scrolling mechanism. Scrolling may be vertical, orhorizontal, or both vertical and horizontal. In the embodiments thatsupport scrolled presentations, the display page loop (FIG. 5) isomitted.

Thus in various embodiments, the operations of layout generator 312 areexecuted as a single thread as follows: identify the content items to beplaced 402, order the content item 406, and place the content items inthe display region according to the ordering of the set of content items(replacing 408 of FIG. 4).

These alternate embodiments correspond to the embodiments described inthe preceding paragraphs, except that (1) the outer display page loop(408 and FIG. 5) is omitted, so that the operations of layout generator312 comprise a nested loop with two levels, (2) flow content items areplaced in the display region in their entireties, (3) criteria foracceptable placement of content items may require that scrolling remainslimited to one dimension, but may not require the complete avoidance ofscrolling, and (4) layout is deemed complete when all content items havebeen placed in the display region. If scrolling is limited to onedimension, one of the criteria for acceptable placement of content itemsis that all content items must visible in the display region withoutintroducing scrolling in the second dimension.

In some embodiments, layout generator 312 allows reordering of thesequence of content items as the outer loop is executed. For example, ifthere has been a failed attempt to place a content item on a displaypage, the content item may be assigned a new position within the list ofcontent items, so that the content item is available for placement onanother display page. In a second example variant, compatible with thefirst example, additional content items may be under considerationbecause of the activity of a separate, concurrently running thread thatdownloads content from one or more Web server sites. In a third examplevariant, compatible with the first two examples, if content items areallowed to appear on multiple display pages, content item ordering mayreflect the appearance histories of content items, so that once acontent item appears on a display page, it remains in the ordered listof content items, but is moved to a position farther from the beginningof the list. In a fourth example variant, compatible with the firstthree examples, suppose that the display page layout in progressincludes blank space that can perfectly accommodate a content itemthat's not at the beginning of the sequence of unplaced content items,while all the content items that appear earlier in the sequence are toobig to fit anywhere on the page. In this case, the content item that canbe accommodated in the blank space is moved to the beginning of thesequence of unplaced content items.

Content item reordering may involve the emission and absorption ofcontent items. A content item may emit a constituent that becomes acontent item to be placed in the list of content items. For example, acontent item corresponding to a flow of text and images may emit animage that becomes a content item to be placed outside the regiondedicated to the flow. Or a flow may emit a flow, as when a flow of textand images emits its images as a new flow. Conversely, a content itemmay absorb another content item, so that the absorbed content item isremoved from the list of content items to be placed. For example, a flowof text and images may absorb an advertisement, with the result that theadvertisement appears inside the region dedicated to the flow.Determination of emissions and absorptions may be sensitive to layoutprogress. For example, if a text flow can absorb an advertisementwithout compromising readability, and if layout has progressed to apoint where the advertisement can't be fit outside the text flow, thenit may be determined that the text flow will absorb the advertisement.

Similarly, in yet other embodiments, layout generator 312 allows thereordering of the sequence of containers as the inner loop is executed.For example, if the content item to be placed has a larger area than canbe accommodated by the container at the beginning of the sequence ofuntried containers, then that container may be deleted from the sequenceof candidate containers.

In still other embodiments, the relationship between the outer contentitem loop and the inner container loop of operations of layout generator312 is reversed—the outer loop drives through containers, while theinner loop drives through content items that are candidates forplacement in the container at hand. Because a container may includemultiple content items, a single pass through the outer loop mayaccomplish multiple placements. These embodiments are well-suited tosituations where maintenance of layout geometry is of prime importance,as when it's desired to have a consistent geometry across display pages.As with the embodiments where the outer loop drives through contentitems and the inner loop drives through containers, both the sequence ofcontent items and the sequence of containers may be reordered as layoutproceeds.

Beyond this, in still other embodiments, the outer loop may drivethrough a sequence that includes both content items and containers,where the sequence may be reordered with each pass, where elements maybe deleted from the sequence with each pass, and where new elements maybe inserted into the sequence with each pass. For a pass over the outerloop that attempts to place a content item, the inner loop is a passover containers. For a pass over the outer loop that attempts to fill acontainer, the inner loop is a pass over content items. The inner loopsequence may be determined dynamically, before the first inner loop passfor a given outer loop pass, and also before each subsequent inner looppass for that outer loop pass. Given that a pass through the outer loopattempts one or more placements involving a container, some passes ofthe inner loop may attempt placements into the container, and somepasses of the inner loop may attempt to place the container into ahigher container, so that the inner loop sequence is a mix of higher andlower display entities. Embodiments with mixed loop sequences arewell-suited to situations like the following: placement of high prioritycontent item I is of prime importance, so I becomes the first element inthe outer loop sequence, and I is placed in container C; once C has onefiller, it becomes of prime importance that C has a second filler forvisual balance, and C becomes the second element in the outer loopsequence.

In the embodiments described so far, only containers that directlycontain content items appear in loop sequences, and higher containers(containers that contain other containers) are placed eagerly as lowercontainers require them. In other embodiments, higher containers mayappear in loop sequences. For example, consistency requirements may makeit important for a particular higher container to appear with minimumtotal area of included display units. Containers in a completed layoutform a hierarchy with the display units corresponding to content itemsas terminal elements. This hierarchy may be constructed top-down orbottom-up, depth-first or breadth-first. Or higher containers may becandidates for inclusion in the outer loop sequence, where themembership of this outer loop sequence and its ordering are determineddynamically as described above. In such embodiments, when a container C(whether a higher container or not) is the subject of a pass through theouter loop, the inner loop might include candidates for placement insideC, or it might include candidate parents for C in the containerhierarchy. In some embodiments, the inner loop sequence might changeduring C's outer loop pass, in such a way that for some inner looppasses, candidate children of C are under consideration, while for otherinner loop passes, candidate parents of C are under consideration.

In addition, in still other embodiments, the operations of layoutgenerator 312 may include layout repair operations 620-622. In anembodiment where the outer loop drives through content items and theinner loop drives through containers, the repair operation 622 may occurwithin the inner placement loop. If no candidate containers canaccommodate the content item to be placed, given the placement decisionsmade for preceding content items, then items already placed may berearranged, effectively changing the earlier placement decisions. Inother embodiments, layout repair steps may occur within the inner loop,or within the outer loop but outside the inner loop. Repairs may begenerated efficiently through diagnosis of layout problems. It should beemphasized that layout repair does not involve backtracking. It appliesdirectly to a layout in its current state.

Initial and subsequent formulations of outer and inner loop sequences,as well as layout repair, may include a variety of diagnostics 410 asinput. Content items may be measured. It may be advantageous to measurea content item multiple times, for example determining the contentitem's height at a range of sample widths. In the interest ofefficiency, estimates may replace actual measurements. For example, thearea to be occupied by a run of text with a uniform font may beestimated based on the font and the length of the text. Another exampleof diagnostic is to determine which containers include blank space, bycomparing a container's measured area with the sum of the areas of itsconstituent content items. Containers with large amounts of blank areamay be favored candidates for receiving additional content items.Another example of a diagnostic is to determine which sets of containerscontribute to making a layout exceed a stipulated limit for a givendimension. Containers that contribute to excess width or height may befavored candidates for giving up content items during a layout repairoperation.

In still other embodiments, threaded versions of variants of layoutgenerator 312 can offer performance advantages. For example, as the mainthread executes the basic nested loop, diagnostics 410 can run on one ormore separate threads, taking into account the progress of the mainthread. Other threads can reorder content items and can reordercontainers, taking into account the progress of the main thread and theresults of diagnostic threads. The innermost loop's work of makingplacements in containers, and percolating the layout effects of theseplacements, can be allocated to multiple threads 412, with the effectsof placement decisions in different containers, possibly includingsubsequent repairs, reported to a thread that makes placement decisions.Other threads can download new content, supplying additional contentitems as input to a thread that reorders content items. As the mainthread works on one display page, other threads can undertakepreparatory work for subsequent display pages. In FIG. 4, the solid lineindicates the only thread in single-threaded embodiments, and indicatesthe main thread in an example of threaded embodiments. The dashed linesindicate subsidiary threads running at lower priorities.

In a layout that exhibits world-within recursion, each node in theworld-within hierarchy has its own container hierarchy. Each node in theworld-within hierarchy is subject to layout according to the embodimentsdescribed above, possibly including embodiments that present content indisplay pages. Layout decisions made at the level of a parent node inthe world-within hierarchy affect possible layouts for the parent'schild nodes, and vice-versa. For example, layout decisions made at theparent level may introduce size constraints to child layouts, and layoutdecisions made at the child level may determine the sizes and shapes ofthe display units to be arranged at the parent level. Global layoutresults will depend on the order in which layout results are committedfor nodes in the world-within hierarchy. Diagnostics for layouts thatexhibit world-within recursion may estimate possible shapes and sizes oflayouts for lower nodes. In some embodiments, estimated shapes and sizesfor nodes at the lowest level of the world-within hierarchy are used toestimate shapes and sizes for nodes at the next higher level, and so on.At the top level of the world-within hierarchy, estimates of shapes andsizes at the next lower level are used to calculate the layout of thetop level according to embodiments in the paragraphs above. With theouter shapes and sizes of layouts for nodes at the next lower level nowfixed, final layouts at the next lower level are calculated according toembodiments in the paragraphs above. Layout proceeds in this fashiondown through the world-within hierarchy until all nodes have been laidout. In cases where layout for a child node cannot be completedacceptably, given the outer size and shape for the child node layoutthat's established in the parent node layout, parent node layout may berepaired directly, with repairs continuing up the world-within hierarchyas required. Layout repair for a parent node proceeds after layout iscomplete for all child nodes. (Layout estimation for sibling nodes inthe world-within hierarchy may be allocated to separate threads, andsimilarly for layout and layout repair.) Thus in these embodiments,layout estimation proceeds bottom-up, then layout based on layoutestimates proceeds top-down, then layout repair proceeds bottom-up. Inother embodiments, layout may proceed bottom-up without any layoutestimation steps, may proceed top-down without any layout estimationsteps, and so on.

Two-dimensional layout of text and graphics may be decomposed into twosub-problems, which may be called “flow layout” and “size, shape, andposition layout.” “Size, shape, and position layout” may be abbreviatedas “SSP layout.” Flow layout involves placing text characters in lines,positioning text lines in columns, positioning images in surroundingtext, and so on. The present invention concerns SSP layout. Its variousembodiments determine the size, shape, and position of display units ina display presentation. Even in its simple manifestations, the SSPlayout problem is exponential, in the sense that the solution space itsexponential in the number of display units to be laid out. Evaluatingall possible solutions is thus impractical. In designing algorithms forthe SSP layout problem, there's a tension between efficiencyrequirements and layout quality requirements. Following what may bereferred to as the search approach, prior art includes a great varietyof algorithms and heuristics for coping with exponential solutionspaces, and includes some applications of these algorithms andheuristics to versions of the SSP layout problem. Some of these priorart applications exhibit unacceptable efficiency, in the worst case oreven in the average case. More typically, they solve impracticallyrestricted instances of the SSP problem, or they produce poor qualityresults with unacceptable frequency. Prior art also includes instancesof a very different approach to SSP layout, where layout proceedsdeterministically, or proceeds deterministically with limitedbacktracking. The principal shared disadvantage of prior artdeterministic approaches is that they produce poor quality layouts inmany cases. The various embodiments of the present invention address therequirement of producing high quality results for a very wide range ofproblem instances. This requirement is a principal motivation for thesearch approach. The various embodiments of the present invention alsoaddress requirements of efficiency, which are a principal motivation ofthe deterministic approach. The various embodiments of the presentinvention proceed for the most part in a deterministic fashion. Withstrictly limited exceptions, there's no search across layoutalternatives. Moreover, execution doesn't backtrack. Instead, anyrequired repair applies directly to results as they stand when the needfor repair is detected. Recall that execution proceeds in three nestedloops, with the outermost paging loop used only for paged presentations.The other two loops may be referred to as the outer loop and the innerloop. Recall further that in some embodiments, both the outer loopsequence and the inner loop sequence may be reconstituted dynamically asexecution proceeds. This reconstitution may take into account the layoutresults that are in place at the time that the reconstitution occurs,and may also take into account the full range of layout desiderata thata search-based algorithm might incorporate in its objective function.

Thus, to summarize, the core of the operations of layout generator 312can be thought of as formation of a valid inner-outer display entitypair, and a determination is made to accept or reject placement of theinner display entity into the outer display entity. The outer displayentity may be a display container, whereas the inner display entity maybe another display container or a content item. Depends on theembodiments, either the outer or the inner display entity may beselected first. The process is repeated with or without switching theorder of inner/outer display entity selection, and ordering/reorderingof content items and/or display containers, modifications of contentitems and/or display containers, as well repair and diagnostics areoptionally performed, as necessary.

FIG. 7 illustrates an architecture view of a computing device 700, suchas a desktop computer or a PDA, suitable for practicing the presentinvention in accordance with one embodiment. Computing device 700 may bea server or a client. Whether as a server or client, computing device700 may be coupled to clients or server via a wireless or wireline basedinterconnection, over one or more private and/or public networks,including the famous public network “Internet”.

As illustrated, for the embodiment, computing device 700 includeselements found in conventional computing device, such asmicro-controller/processor 702, digital signal processor (DSP) 704,non-volatile memory 706, display 708, input keys 710 (such as keypad,select button, D-unit), and transmit/receive (TX/RX) 712, coupled toeach other via bus 714, which may be a single bus or an hierarchy ofbridged buses. Further, non-volatile memory 706 includes operating logic720 adapted to implement the earlier described layout generator 312,layout interpreter 315 and/or render engine 316, in and ofitself/themselves or as part of one or more larger components. Theimplementation may be via any one of a number programming languages,assembly, C, and so forth.

In alternate embodiments, all or portions of the operating logic 720maybe implemented in hardware, firmware, or combination thereof.Hardware implementations may be in the form of application specificintegrated circuit (ASIC), reconfigured reconfigurable circuits (such asField Programming Field Array (FPGA)), and so forth.

FIGS. 8 a-8 c illustrate a first example problem the present inventionmay be applied to address, which is to permit full use of the availableareas of computer display windows.

Currently, computer systems may fail to take full advantage of theavailable area of display windows to display information. For example,Web sites cannot take full advantage of available area of client browserwindows to display advertisements. Client browser windows use a varietyof screen resolutions and window sizes. Web pages may be authored usingsmall fixed widths, so that the majority of clients can view the pageswithout horizontal scrolling, as illustrated in FIG. 8 a. But thenclients with larger displays have unused real estate, as illustrated inFIG. 8 b.

HTML and CSS allow Web pages to be authored with percent widths. AnHTML/CSS Web page can stretch to fit large client display widths.However, layouts with percent widths can generate internal wasted realestate, as illustrated in FIG. 8 c. Even if no real estate is wasted,percent widths do nothing to use increased real estate for additionalinformation display.

FIGS. 9 a-9 c illustrate a second example application of the presentinvention to accommodate display items of different sizes withincomputer display windows.

FIG. 9 a illustrates a prior art Web page with three advertisements.

FIG. 9 b illustrates a prior art Web page with severe layout problemsresulting from substituting the advertisements in FIG. 9 a withadvertisements of different dimensions.

FIG. 9 c illustrates how the present invention can accommodate the samesubstitutions shown in FIG. 9 b, in various embodiments.

FIGS. 10 a-10 f illustrate a third example application of the presentinvention to permit information display in computer display windowswithout scrolling.

FIGS. 10 a and 10 b illustrate a Web-based newspaper article withadvertisements, presented according to prior art. (The illustrative textis selected from Discours de la Méthode, by Descartes, rather than froman actual or made-up news article.) The article is spread across two Webpages with fixed width and height. The two Web pages have identicallayouts, although they contain different advertisements. The browserwindow is wider and shorter than the Web page layout. In both FIG. 10 aand FIG. 10 b, the dashed line indicates the bottom of the browserwindow. The total number of advertisements displayed in the two Webpages is 14. However, only 6 of the advertisements appear entirely abovethe fold in the browser window. The user can read the entire articlewithout bringing any of the remaining 8 advertisements into completeview.

FIGS. 10 c-10 f illustrate one way in which the same newspaper articlemay be laid out according to the present invention. The article isspread across four Web pages, each of which has height and widthcorresponding to the height and width of the display window. The layoutsof the four Web pages are different from each other. These layouts havebeen generated in response to the publisher's advertising displayrequirements, which may be sensitive to factors such as advertisementpricing and user targeting, and which may include preferences such asthe placement of higher-priced and more-specifically-targetedadvertisements closer to the beginning of the article. Advertisingdisplay requirements are reflected not only in the selection ofadvertisements, but also in the positions the selected advertisementstake within the initial ordering of content items. FIGS. 10 c-10 fillustrate possible results when a publisher prefers to have moreadvertisements with smaller dimensions, rather than fewer advertisementswith larger dimensions. The total number of advertisements that appearin the four Web pages is 37, all of which appear above the fold. It maybe emphasized that this is a single illustration of the the presentinvention applied to the presentation of a Web-based newspaper articlein a browser window. Different users, with different browser displayparameters and different targeting profiles, can be served verydifferent selections of advertisement sizes, because the advertisementsaren't constrained to fit in fixed-size slots within fixed layouts.Basic layout requirements will vary from publisher to publisher.Advertising display requirements will likewise vary from publisher topublisher.

The above are just examples and not exhaustive of all possibleapplications of embodiments of the present invention.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a wide variety of alternate and/or equivalent implementations maybe substituted for the specific embodiments shown and described, withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the embodimentsdiscussed herein. Therefore, it is manifestly intended that thisinvention be limited only by the claims and the equivalents thereof.

1. A processor implemented method for automated layout of a plurality ofcontent items, comprising: forming by a layout generator operated by aprocessor, an inner-outer display entity pair having an inner displayentity and an outer display entity, the outer display entity being adisplay container, and the inner display entity being a selected one ofone of said content items and another display container; accepting orrejecting placement by the layout generator of the inner display entityinto the outer display entity based at least in part on one or morelayout placement criteria; and repeating said forming and said acceptingor rejecting at least one other time if layout of the content items isincomplete and another inner-outer display entity pair can be formed. 2.The method of claim 1, wherein said forming comprises the layoutgenerator selecting the outer display entity, followed by the layoutgenerator selecting the inner display entity.
 3. The method of claim 1,wherein said forming comprises the layout generator selecting the innerdisplay entity, followed by the layout generator selecting the outerdisplay entity.
 4. The method of claim 1, wherein said forming comprisesthe layout generator selecting a display container, followed by thelayout generator selecting another display container to contain or becontained by the earlier selected display container.
 5. The method ofclaim 1, wherein said forming comprises the layout generator firstselecting a selected one of the inner display entity or the outerdisplay entity by an outer execution loop, followed by selecting theother of the inner and outer display entities by an inner execution looplooping within the outer execution loop.
 6. The method of claim 1,wherein said forming comprises the layout generator first selecting aselected one of the inner display entity or the outer display entity byan inner execution loop, and then selecting the other of the inner andouter display entities by an outer execution loop looping outside of theinner execution loop.
 7. The method of claim 1, wherein said one or morelayout placement criteria include at least one of: a criterionassociated with whether scrolling is required for a content item to beplaced in a display container, when the inner-outer pair is a contentitem-display container pair, a criterion associated with placement ofsubconstituents of a content item, when the inner-outer pair is acontent item-display container pair, a criterion associated with displayspace utilization, and a criterion associated with display aesthetics.8. The method of claim 1, wherein said repeating comprises the layoutgenerator, on rejecting the placement of the inner display entity in theouter display entity, forming another inner-outer display entity pair byreplacing one of the display entities of the rejected inner-outerdisplay entity pair, and accepting or rejecting placement of the innerdisplay entity of the another inner-outer display entity pair into theouter display entity of the another inner-outer display entity pairbased at least in part on one or more layout placement criteria.
 9. Themethod of claim 8, wherein said replacing comprises the layout generatorselecting another inner display entity to form the another inner-outerdisplay entity pair with the outer display entity of the rejectedinner-outer display entity pair, or selecting another outer displayentity to form the another inner-outer display entity pair with theinner display entity of the rejected inner-outer display entity pair.10. The method of claim 8, wherein the method further comprises thelayout generator, on rejecting the placement of the inner display entityof the another inner-outer display entity pair in the outer displayentity of the another inner-outer display entity pair, relocating aprevious placement of a content item.
 11. The method of claim 10 furthercomprising the layout generator performing a plurality of diagnostics,and identifying the previously placed content item to be relocated basedat least in part on diagnostic data obtained from performance of saiddiagnostics.
 12. The method of claim 1, wherein the method furthercomprises the layout generator, on accepting the placement of the innerdisplay entity in the outer display entity, prior to said repeating,forming another inner-outer display entity pair with the inner displayentity of the previously accepted inner-outer display entity pair andanother outer display entity, accepting or rejecting placement of theinner display entity of the previously accepted inner-outer displayentity pair into the another outer display entity based at least in parton one or more layout placement criteria that includes layout placementcriteria of whether the placement represented by the another inner-outerdisplay entity pair is better than the placement represented by theprevious inner-outer display entity pair, the placement represented bythe another inner-outer display entity pair supersedes the placementrepresented by the previous inner-outer display entity pair if placementof the inner display entity of the previously accepted inner-outerdisplay entity pair into the another outer display entity is accepted.13. The method of claim 1, wherein said repeating comprises the layoutgenerator, on accepting the placement of the inner display entity thatis another display container in the outer display entity, forminganother inner-outer display entity pair having another inner display andanother outer display entity, and accepting or rejecting placement ofthe another inner display entity into the another outer display entitybased at least in part on one or more layout placement criteria.
 14. Themethod of claim 13, wherein the another inner display entity of theanother inner-outer display entity pair is the outer display entity ofthe inner-outer display entity pair.
 15. The method of claim 13, whereinthe method further comprises the layout generator evaluating one or morelayout completion criteria.
 16. The method of claim 14, wherein the oneor more layout completion criteria comprise at least one of: a criterionassociate with placement of a sufficient set of content items, acriterion associated with display space utilization, and a criterionassociated with display aesthetics.
 17. The method of claim 1, whereinthe method further comprises the layout generator modifying at least oneof inner and outer display entities of the inner-outer display entitypair, and the accepting or rejecting is based on the modifiedinner-outer display entity pair.
 18. The method of claim 17, whereinsaid modifying comprises at least a selected one of: converting acontent item from absolute to percentage sizing, providing a graphictreatment to a content item, relocating a display entity, modifying asize of a display entity, and modifying a shape of a display entity. 19.The method of claim 1, wherein the outer display entity is a displaycontainer, and the method further comprises the layout generatorcreating the display container.
 20. The method of claim 1, furthercomprises the layout generator ordering content items prior to or afterperforming said forming and accepting, or said forming and rejecting.21. The method of claim 20 wherein said ordering is performed based onvalues of the content items and/or diagnostic data gathered on thecontent items.
 22. The method of claim 1, further comprises the layoutgenerator ordering display containers prior to or after performing saidforming and accepting, or said forming and rejecting.
 23. The method ofclaim 22 wherein said ordering is performed based on remaining contentitem holding capacity of the display containers.
 24. The method of claim1, wherein said forming comprises the layout generator selecting theinner display entity by a first execution thread, and selecting theouter display entity by a second execution thread, said first and secondexecution threads being different execution threads.
 25. The method ofclaim 1, further comprising the layout generator receiving a pluralityof content items from one or more sources selected from the groupconsisting of an application, a content cache, and a content server. 26.The method of claim 25, wherein said forming and accepting, or saidforming and rejecting are performed to generate a rendering layoutspecification for rendering the plurality of content items.
 27. Themethod of claim 26, further comprising a render engine processing thegenerated rendering layout specification, and rendering the contentitems in accordance with the rendering layout specification.
 28. Themethod of claim 25, wherein said rendering comprises the render enginerendering on a selected one of a display surface of a display device, alogical display pane, a portion of a display window, an electronic page,a portion of an electronic page, a portion of a printed page and aprinted page.
 29. A computer readable medium comprising a plurality ofprogramming instructions configured to program an apparatus having aprocessor to enable the apparatus to practice the processor implementedmethod as set forth in claim
 1. 30. An apparatus comprising: aprocessor; an inner-outer display entity pair formation module operatedby the processor to successively form one or more inner-outer displayairs for automated layout of a plurality of content item, eachinner-outer display entity pair having an inner display entity and anouter display entity, the outer display entity being a displaycontainer, and the inner display entity being a selected one of saidcontent items and another display container; and an acceptance orrejection module operated by the processor to successively accept orreject placement of the inner display entity of each inner-outer displayentity pair into the outer display entity of the inner-outer displayentity pair, based at least in part on one or more layout placementcriteria.
 31. The apparatus of claim 30, wherein the apparatuscomprising a layout generator comprising the inner-outer display entitypair formation module and the acceptance or rejection module.
 32. Theapparatus of claim 31, wherein the layout generator is configured toperform said forming and accepting, or said forming and rejecting togenerate a rendering layout specification for rendering the plurality ofcontent items.
 33. The apparatus of claim 31, further comprising arender engine coupled to the layout generator, and operated by theprocessor, to process the generated rendering layout specification, andrender the content items in accordance with the rendering layoutspecification.
 34. The apparatus of claim 30, wherein each displaycontainer having one or more display units of a display presentation,the layout placement criteria including a criterion associated withplacement of subconstituents of a content item in a display unit, whenthe inner-outer pair is a content item-display container pair and thecontent item has subconstituents, and the inner-outer display entitypair formation module and the acceptance or rejection module areoperated by the processor as two execution threads.